Woah, amazing work cropping inside a video. Best of all, I think you could recreate all of that in javascript with canvas ( ofc, after you manually set the video file ).

Either directly edit the video live, but I’m not sure how well will that work (usually freezes the browser ) or slow version with js workers ( but takes some time ).
Or 2nd version to crop each frame from video with canvas and to animate it:
either display each image with 1000 ms timeouts for each or convert somehow to gif (i’m not sure about this).